They might be using a picture that is rights/royalty-free, or even something they've paid for because they don't have the equipment to shoot their own teas. Rishi probably has paid for the use of that photo, since it's on their packaging. In the Zen organics picture, it looks more like the picture is being use for decorative purposes than actually showing off their particular matcha. You might want to email each company and ask them to send you a picture of their matcha, if you're really very interested.

If you do an image search, that image shows up on many sites, leading me to believe that it is a stock image. Not to say that IT did NOT steal it, (since they've demonstrated that they WILL lift images without permission,) just to say that Zen possibly doesn't own the image, but has purchased usage rights, as have (apparently) a number of other companies.